The present invention relates generally to devices for re-sharpening machine tools, and more particularly to a completely automated system which verifies the identity and geometry of drill bits, re-sharpens the drill bits to within closely held tolerances, verifies re-sharpened drill bit tolerances, adjusts the positioning of a locating ring disposed upon the shank of the re-sharpened drill bits, cleans the re-sharpened drill bits and subsequently packages the same.
The manufacture of printed circuit boards has experienced considerable improvement over recent years. Technological advancements in chemistry, machinery, and materials have resulted in the ability to consistently produce large volumes of printed circuit boards with dense circuitry patterns on a highly efficient basis. One particular area of progress has been in the drilling process associated with printed circuit boards. An individual circuit board typically includes thousands of small-diameter drilled holes which are used to connect various components to the board by accommodating the leads or pins thereof, to connect the circuitry traces of one layer to another, to provide reference points for subsequent processing, and to assist in mounting the complete circuit board within its final housing. In one currently known circuit board manufacturing process, a plurality of circuit boards are drilled simultaneously by maintaining the circuit boards in a contiguous, overlapped orientation. In another currently known fabrication technique, several circuit boards are placed on a panel for processing, with a single panel typically including tens of thousands of drilled holes.
As will be recognized, due to the extremely small diameter of the holes typically drilled in the printed circuit boards, the associated drill bits are formed having small diameter cutting tips and are made of an extremely hard, wear resistant material such as tungsten carbide. Though this material is resistant to wear, after a certain number of drilled holes (xe2x80x9chitsxe2x80x9d), the drill bit will typically deteriorate and will no longer be sharp enough to maintain the diameter and tolerance requirements for subsequent holes. Through experience, circuit board manufactures have approximated the rate at which drill bits dull. Based upon this wear rate, the drill bit is typically replaced after a certain number of hits.
During the printed circuit board manufacturing process, the depth to which the cutting tip of the drill bit penetrates, i.e., extends into, the circuit board(s) must also be tightly controlled. In this respect, the drill bits used to facilitate the drilling operation are typically provided with a locating ring disposed about the shank portion thereof which serves as a stop for accurately locating the drill bit, the collet, or the tool holder of the rotary drilling apparatus. Due to the importance of tightly controlling the penetration depth of the cutting tip of the drill bit into the circuit board(s), the distance separating the cutting tip from the locating ring must itself be tightly controlled, thus necessitating the precise positioning of the locating ring upon the shank portion of the drill bit.
In view of the difficulty and expense associated with the manufacture of carbide drill bits with small diameter cutting tips, once the cutting tip of the drill bit becomes dull, the same is typically re-sharpened rather than being discarded. As will be recognized, due to the importance of drilling all the holes within the circuit board(s) within closely held tolerances, the re-sharpening of the cutting tip of the drill bit must be accomplished in a precise, highly accurate manner. Additionally, since the re-sharpening procedure often results in a slight loss of length from the cutting tip region of the drill bit, the distance separating the cutting tip from the locating ring must be maintained within a certain, tightly controlled range. In this respect, the shortening of the drill bit which occurs as a result of the re-sharpening procedure requires that the position of the locating ring upon the shank portion be adjusted so as to once again achieve the desired separation distance between the locating ring and the sharpened cutting tip.
The re-positioning of the locating ring upon the shank portion of the drill bit is typically accomplished manually through the utilization of conventional measurement techniques and devices such as calipers. Additionally, the re-sharpening of the cutting tip of the drill bit and subsequent measurement thereof to ensure compliance with tolerance requirements are often accomplished manually. However, as will be recognized, such manual re-positioning and re-sharpening techniques are extremely time consuming and thus expensive, and oftentimes do not accomplish the positioning of the locating ring relative the cutting tip and/or the re-sharpening of the cutting tip with the degree of accuracy needed to ensure that the subsequent drilling operation will be properly conducted.
There has yet to be developed in the prior art an completely automated system for accomplishing the verification of identity and differing geometries of various drill bits and the re-sharpening and re-positioning functions described above. One of the difficulties in automating the re-sharpening process is that the size and condition of the cutting tip of the drill bit often varies. In this respect, the cutting tip may be dirty, worn, undersize in diameter and/or length, chipped, or broken. Additionally, drill bits are typically sent for re-sharpening in large quantities, with such quantities including drill bits that are from different manufacturers, have different dates of original manufacture, are of differing styles and/or series, or are being subjected to a first or subsequent re-sharpening procedure.
The present invention specifically addresses the above-described deficiencies and obstacles by providing a completely automated system which automatically verifies the identity and geometry of drill bits, re-sharpens the cutting tip of a drill bit to within closely held tolerances, and accurately adjusts the positioning of the locating ring upon the drill bit subsequent to the re-sharpening of the cutting tip thereof.
In accordance with the present invention, there is provided an automated apparatus for verifying the identity and geometry of drill bits and re-sharpening the drill bit having a shank portion including a locating ring positioned thereupon, and a fluted portion which defines a cutting tip of the drill bit. In addition to functioning to re-sharpen the cutting tip of the drill bit, the present automated apparatus functions to adjust the position of the locating ring relative to the cutting tip subsequent to the re-sharpening thereof.
In the preferred embodiment, the automated apparatus comprises a housing or base table having at least one and preferably a pair of cassette trays attached thereto, each of which is sized and configured to accommodate multiple drill bit containers. Each of the drill bit containers includes a plurality of drill bits stored therewithin. Also attached to the housing is a pair of grinding assemblies, each of which is used to grind the cutting tip of a drill bit, and a pair of vision or optical assemblies, each of which is used to conduct an initial verification of the identity and geometry of the drill bit inspection of the cutting tip of a drill bit prior to the grinding thereof and a final inspection of the cutting tip subsequent to the grinding thereof. In addition to the grinding and optical assemblies, attached to the housing is a pair of primary cleaning assemblies which are each used for cleaning the cutting tip of a drill bit prior to the initial inspection thereof, and a pair of secondary cleaning assemblies which are each used for cleaning the cutting tip of a drill bit prior to the final inspection thereof. Also attached to the housing is a pair of inversion assemblies for selectively directing one of the shank portion and the fluted portion of a drill bit generally vertically upwardly, and at least one bumping assembly which is used for adjusting the position of the locating ring of a drill bit relative to its cutting tip subsequent to the final inspection thereof.
The automated apparatus of the present invention further comprises a pair of workhead assemblies which are each movably attached to the housing and used for selectively transporting a drill bit between respective ones of the optical, grinding, and secondary-cleaning assemblies. Also movably or rotatably attached to the housing is a robotic loader assembly of the automated apparatus which is used to selectively transport drill bits from the cassette trays to respective ones of the inversion assemblies if required by the orientation of the drill bits within the drill bit containers, from the cassette trays or inversion assemblies to respective ones of the primary cleaning assemblies, from the primary cleaning assemblies to respective ones of the inversion assemblies, from the inversion assemblies to respective ones of the workhead assemblies, from the workhead assemblies to the bumping assembly, and from the bumping assembly back to respective ones of the cassette trays.
In the present automated apparatus, a programmable control device is electrically interfaced to the grinding, optical, secondary cleaning, inversion, bumping, workhead, and loader assemblies to control and coordinate the operations thereof in a manner allowing the cutting head re-sharpening and locating ring re-positioning processes to be conducted simultaneously on at least two drill bits. In this respect, the control device is operable to cause the loader assembly to remove the drill bits from each drill bit container one at a time, and return each of the drill bits to the drill bit container from which it was removed subsequent to the final inspection of the cutting tip or the re-positioning of the locating ring.
In the preferred embodiment; the loader assembly of the automated apparatus comprises a robotic arm which is rotatable about first, second and third generally parallel loader axes, and movable linearly (i.e., upwardly and downwardly) along the third loader axis. Attached to the robotic arm is a gripper which is adapted to receive and releasably hold one or two drill bits, and is pivotally movable relative to the third loader axis. The gripper itself comprises a pair of shaft members which are pivotally connected to the robotic arm. Each of the shaft members has an aperture extending therethrough which is sized and configured to receive the shank portion of a drill bit. The gripper further comprises a rotary actuator member which is connected to the robotic arm and mechanically coupled to the shaft members in a manner wherein the movement of the actuator results in the concurrent pivotal movement of the shaft members relative to the robotic arm. In addition to the shaft and actuator members, the gripper comprises an elongate vacuum tube which is fluidly connected to the apertures for selectively creating negative pressure therewithin. The creation of a vacuum within each of the apertures subsequent to the receipt of the shank portion of a drill bit thereinto facilitates the retention of the drill bit within the gripper of the loader assembly.
Each of the optical assemblies of the automated apparatus comprises top and front cameras for generating images which are used to determine the overall length of the drill bit, the diameter and geometry of the cutting tip thereof, and the condition of the margins thereof. The images generated by the top and front cameras are further used to index the cutting tip to selected reference points. In addition to the top and front cameras, each optical assembly further includes an illumination array for illuminating the fluted portion and the cutting tip, and control logic which is operative to process and interpret the images generated by the top and front cameras. The control logic of each of the optical assemblies also interacts with the control device in a manner facilitating the regulation of the movement of each of the workhead assemblies in a prescribed manner based on the generated images.
Each of the grinding assemblies comprises at least one grinder motor having a grinder head rotatably connected thereto. The grinder head itself defines a grinding face. Each grinding assembly further comprises an adjustment mechanism which is attached to the grinder motor and is operative to selectively move the grinder head into and out of contact with the cutting tip of the drill bit based upon the level of contact pressure exerted by the cutting tip against the grinding face. The adjustment mechanism itself comprises a housing having an elongate ball screw rotatably mounted thereto. Mechanically coupled to the ball screw is a stepper motor which is operative to selectively rotate the ball screw in either a first direction or a second direction opposite the first direction. Additionally, cooperatively engaged to the ball screw is a linear bearing. In the adjustment mechanism, the rotation of the ball screw in the first direction facilitates the movement of the linear bearing toward a respective workhead assembly. Conversely, the rotation of the ball screw in the second direction facilitates the movement of the linear bearing away from the corresponding workhead assembly. The grinder motor is itself attached to the linear bearing.
Each of the primary cleaning assemblies of the automated apparatus comprises a bath having a quantity of cleaning putty disposed therein. The cutting tip of a drill bit is insertable into and removable from within the cleaning putty of each primary cleaning assembly via the loader assembly. Additionally, each of the secondary cleaning assemblies comprises a base member having a conveyor member movably attached thereto. The conveyor member is selectively movable between extended and retracted positions relative to the base member, and includes a quantity of cleaning putty disposed thereon. In addition to the base and conveyor members, each secondary cleaning assembly comprises an indexing member which is attached to the base member and operable to index the conveyor member a prescribed incremental distance when the conveyor member is moved from its extended position to its retracted position. The cutting tip of a drill bit is insertable into the cleaning putty of a respective one of the secondary cleaning assemblies by a respective one of the workhead assemblies, with such insertion occurring immediately prior to the final inspection of the cutting tip by a respective one of the optical assemblies.
Each of the workhead assemblies of the automated apparatus comprises a base member which is reciprocally moveable relative to the housing along a first axis. Rotatably connected to the base member is a swivel member which is rotatable about a second axis extending in generally perpendicular relation to the first axis. Movably attached to the swivel member is a collet member which is adapted to receive and releasably hold the shank portion of a drill bit. The collet member is reciprocally movable along and rotatable about a third axis which extends in generally perpendicular relation to the second axis. The insertion of a drill bit into the collet and the removal of the drill bit from therewithin is accomplished via the loader assembly. Each workhead assembly further comprises a support member which is attached to the base member and receives and supports a portion of the collet member when the cutting tip is being ground by a respective one of the grinding assemblies.
The bumping assembly of the automated apparatus comprises a drill seat which is attached to the housing for slidably receiving the shank portion of a drill bit. In addition to the drill seat, the bumping assembly comprises an adjustment mechanism which is attached to the housing and used for positioning the cutting tip a desired separation distance from the drill seat, and a reciprocal ram assembly which is movably attached to the housing and used for selectively bumping the locating ring into abutting contact with the drill seat subsequent to the shank portion being inserted into the drill seat and the cutting tip being positioned at the separation distance from the drill seat. The drill bit is insertable into and removable from within the drill seat via the loader assembly.
Each of the inversion assemblies of the automated apparatus comprises a base member and a rotatable inversion arm which is attached to the base member and adapted to receive a drill bit. In addition to the base member and inversion arm, each of the inversion assemblies comprises a locking pin which is attached to the base member for maintaining the drill bit within the inversion arm. Also attached to the base member is an air stream generator of the inversion assembly which is used to remove residual putty from the cutting tip of the drill bit within the inversion arm. Drill bits are inserted into and removed from within the inversion arm of each of the inversion assemblies via the loader assembly.
Further in accordance with the present invention, there is provided an automated method of re-sharpening a drill bit having a shank portion which includes a locating ring positioned thereupon and a fluted portion which defines a pair of margins and a cutting tip. The present method employs the use of an automated re-sharpening apparatus which includes a pair of cassette trays, a pair of grinding assemblies, a pair of optical assemblies, a pair of primary cleaning assemblies, a pair of secondary cleaning assemblies, a pair of workhead assemblies, a bumping assembly, and a loader assembly. In addition to re-sharpening the cutting tip of the drill bit, the present method also achieves the re-positioning of the locating ring relative to the cutting tip if necessitated by the re-sharpening thereof.
The present method comprises the initial step of positioning at least one, and preferably multiple drill bit containers onto respective ones of the cassette trays, with each of the drill bit containers including a plurality of drill bits stored therewithin. Thereafter, the drill bits are removed from each drill bit container one at a time via the loader assembly. Such removal is accomplished by advancing the loader assembly over the drill bit and into contact with the locating ring positioned upon the shank portion thereof. Thereafter, negative pressure is created within the loader assembly at a level sufficient to retain the drill bit therewithin.
The drill bits may be oriented within each of the drill bit containers such that either the shank portion or fluted portion thereof is directed generally vertically upwardly. If, during the removal of a drill bit from within a respective drill bit container, the loader assembly is advanced over the fluted portion, the drill bit is thereafter inserted into the rotatable arm of a respective one of the inversion assemblies via the loader assembly such that the fluted portion is directed generally vertically upwardly. Thereafter, the pressure within the loader assembly is equalized, with the loader assembly then being retracted away from the drill bit. The inversion arm is then rotated such that the shank portion is directed generally vertically upwardly. Subsequent to this xe2x80x9cflippingxe2x80x9d of the drill bit, the loader assembly is advanced over the shank portion thereof and into contact with the locating ring positioned thereupon. Negative pressure is then again created within the loader assembly at a level sufficient to retain the drill bit therewithin. The drill bit is then removed from within the inversion arm via the loader assembly.
After the drill bit has been inverted and re-grasped by the loader assembly in the above-described manner, the fluted portion of the drill bit protrudes from the loader assembly. The cutting tip of the drill bit is then inserted into and removed from within the quantity of cleaning putty of one of the primary cleaning assemblies via the loader assembly. If, during the removal of the drill bit from within a respective one of the drill bit containers, the loader assembly is advanced over the shank portion of the drill bit rather than the fluted portion thereof, the drill bit need not be inverted prior to the cleaning of the cutting tip thereof via a respective one of the primary cleaning assemblies since the fluted portion already protrudes from the loader assembly. Rather, subsequent to the removal of the drill bit from within a respective one of the drill bit containers, the cutting tip thereof is inserted into and removed from within the quantity of cleaning putty of one of the primary cleaning assemblies via the loader assembly.
After being cleaned by one of the primary cleaning assemblies, the drill bit is inserted into the rotatable arm of a respective one of the inversion assemblies via the loader assembly such that the shank portion thereof is directed generally vertically upwardly. The pressure within the loader assembly is then equalized, with the loader assembly then being retracted from the drill bit. The air stream generator is then used to blow air onto the cutting tip of the drill bit to remove any residual cleaning putty therefrom. Thereafter, the inversion arm is rotated such that the fluted portion of the drill bit is directed generally vertically upwardly. The loader assembly is then advanced over the fluted portion of the drill bit and into contact with the locating ring positioned upon the shank portion thereof. Negative pressure is then again created within the loader assembly at a level sufficient to retain the drill bit therewithin, with the drill bit then being removed from within the inversion arm via the loader assembly.
After being removed from within the inversion assembly, the drill bit is transferred from the loader assembly to a respective one of the workhead assemblies. More particularly, the shank portion of the drill bit is inserted into a respective one of the workhead assemblies via the loader assembly. Once releasably held within a respective workhead assembly, the fluted portion of each drill bit is inserted into the interior of a respective one of the optical assemblies thereby.
Once inserted into a respective optical assembly, the overall length of the drill bit is determined, as is the diameter of the cutting tip and the condition of the margins. Thereafter, the cutting tip is indexed to a prescribed position. The determination of the overall length of the drill bit is preferably accomplished by indexing the cutting tip to a first reference point on a second reference axis generated by the control logic of the optical assembly via the workhead assembly. This step is followed by determining the distance between the first reference point and a point of intersection between the first reference axis and a second reference axis also generated by the control logic of the optical assembly. The control logic of the optical assembly is further operative to generate a reference line and a target line, with the step of indexing the cutting tip to a prescribed position preferably being initiated by the generation of the reference line along the cutting tip of the drill bit. Thereafter, the drill bit is rotated via the workhead assembly to adjust the angular orientation of the reference line relative to a third reference axis generated by the control logic of the optical assembly to within a prescribed range. The cutting tip is then indexed to a second reference point on the second reference axis, with the target line thereafter being generated along one of the margins of the fluted portion. Finally, the drill bit is rotated via the workhead assembly as needed to cause the target line to cross the point of intersection between the first and second reference axes. The drill bit is thereafter removed from within the optical assembly via the workhead assembly.
After the initial evaluation of the fluted portion and the cutting tip of each drill bit has been completed by a respective optical assembly, the cutting tip of each drill bit is ground via a respective one of the grinding assemblies. In particular, the cutting tip of each drill bit is moved into contact with a respective grinding assembly via the workhead assembly in which the drill bit is releasably held. After its initial movement into the grinding assembly, the cutting tip of the drill bit is backed away therefrom via the workhead assembly, and then rotated approximately 180xc2x0 thereby. Subsequent to such rotation, the cutting tip is then moved back into contact with and thereafter drawn back away from the grinding assembly. Importantly, the grinding operation conducted on the cutting tip of each drill bit by a respective one of the grinding assemblies is governed by the initial evaluation of the fluted portion and cutting tip of the drill bit by the corresponding optical assembly. Additionally, when the cutting tip of each drill bit is moved into contact with a respective one of the grinding assemblies, a portion of the collet member of the associated workhead assembly is advanced through and supported by the support member of the workhead assembly to reduce the vibration of the cutting tip during the grinding process. During each of the grinding operations described above, the grinding assembly may be retracted away from the cutting tip of the drill bit in the event the contact pressure between the cutting tip and the grinding assembly exceeds a prescribed level.
Subsequent to being ground, the drill bits are carried by the workhead assemblies in which they are releasably held to respective ones of the secondary cleaning assemblies. As the workhead assembly approaches a respective secondary cleaning assembly, the conveyor member of the secondary cleaning assembly is actuated to its extended position, thus placing a portion of the cleaning putty disposed thereon into horizontal alignment with the cutting tip of the drill bit. The cutting tip of the drill bit is then inserted into the cleaning putty of the secondary cleaning assembly by the associated workhead assembly. The conveyor member of the secondary cleaning assembly is then actuated back to its retracted position. Importantly, the movement of the conveyor member back to its retracted position causes the indexing member attached to the base member of the secondary cleaning assembly to index the conveyor member a prescribed incremental distance. Such movement of the conveyor member causes the cutting tips of subsequently cleaned drill bits to be inserted into different portions of the cleaning putty disposed upon the conveyor member.
After being cleaned by respective ones of the secondary cleaning assemblies, the drill bits are re-inserted by the workhead assemblies into respective ones of the optical assemblies. Within each optical assembly, a final evaluation of the drill bit is conducted. In the final evaluation, the overall length of the drill bit is determined, as is the geometry of the cutting tip and condition of the margins thereof. The determination of the overall length of the drill bit is accomplished in the same manner previously described in relation to the initial evaluation. Subsequent to the completion of such measurements, the drill bit is then removed from within the optical assembly via the workhead assembly in which it is releasably held. The final evaluation of each drill bit also includes a determination as to whether the locating ring of the drill bit is properly positioned relative to the cutting tip thereof.
If it is determined that the positioning of the locating ring relative to the cutting tip must be adjusted, the drill bit is transported from its associated workhead assembly to the bumper assembly via the loader assembly. In particular, the shank portion of the drill bit is inserted into a drill seat of the bumping assembly, with the cutting tip then being positioned at a desired separation distance from the drill seat. Thereafter, the locating ring is bumped into abutting contact with the drill seat. Subsequent to the completion of this bumping operation, the drill bit is transported from the bumping assembly back to a respective one of the cassette trays via the loader assembly. More particularly, the drill bit is returned by the loader assembly to the precise location in the drill bit container from which it was initially removed. As will be recognized, if during the final evaluation of the drill bit it is determined that the position of the locating ring need not be adjusted, the drill bit is transported directly from the workhead assembly to the proper cassette tray by the loader assembly. Additionally, if during the final evaluation of the drill bit it is determined that there is a fault in the geometry of its cutting tip, the drill bit is not transported to the bumping assembly or to a drill bit container on one of the cassette trays, but rather is ejected to a separate location by the loader assembly.
In the present method, the drill bits need not necessarily be removed from and returned to the cassette trays, and in particular the drill bit containers positioned thereon, but rather may be removed from any pick-up location and returned to any drop-off location. Additionally, in the present method, data corresponding to the initial and final evaluations of each of the drill bits processed by the re-sharpening apparatus is preferably stored within the control device. This data may be used to facilitate the generation of a statistical process control report regarding the processed drill bits. This data may also be used to generate a used drill profile which may itself be used to adjust the manner in which the cutting tips of subsequently processed drill bits are ground by the re-sharpening apparatus. Moreover, the data generated and stored in relation to the drill bits may be used to facilitate the sorting thereof in a manner wherein the drill bits are transported to respective ones of multiple drop-off locations according to the final evaluations related thereto.
In the above-described steps of the present method wherein the loader assembly is used to transport the drill bit between the workhead assemblies and the bumping assembly and between the bumping assembly and respective ones of the cassette trays, such transport is accomplished in the same manner previously described in relation to the removal of the drill bit from one of the cassette trays via the loader assembly, the insertion of the drill bit into and the removal of the drill bit from within a respective one of the inversion assemblies by the loader assembly both prior and subsequent to the initial cleaning of the cutting tip thereof, and the transfer of the drill bit from the loader assembly to a respective one of the workhead assemblies. More particularly, the loader assembly is initially advanced over the fluted portion of the drill bit and into contact with the locating ring positioned upon the shank portion. Thereafter, negative pressure is created within the loader assembly at a level sufficient to retain the drill bit therewithin. After the shank portion of the drill bit has been inserted into either a workhead assembly, the drill seat of the bumping assembly, or the drill bit container, the pressure within the loader assembly is equalized, with the loader assembly then being retracted from the drill bit.
For each drill bit to be inserted into and removed from within the inversion arm of an inversion assembly, the drill seat of the bumping assembly, and the drill bit container, the drill bit must be maintained in a generally vertical orientation by the loader assembly. However, to be inserted into and removed from within each workhead assembly, the drill bit must be maintained in a generally horizontal orientation by the loader assembly. As such, the loader assembly is adapted to pivot to accomplish the extension of the drill bit either vertically or horizontally as needed.